"Happy birfday to my #numberonesie," the actress, 24, captioned the Instagram shot, alongside a pair of blue hearts and an emoji of a couple. In the picture, the birthday boy, 25, kisses his girlfriend on the side of her head.
The new couple, who play onscreen love interests on Scream Queens, were first linked in December when they were spotted kissing at the Fox comedy's wrap party in West Hollywood. Costar Keke Palmer documented the sweet moment on her Snapchat account on December 4.
Last month, Lourd and Lautner jetted off to Cabo San Lucas, Mexico, following the back-to-back deaths of her mother, Carrie Fisher, and grandmother Debbie Reynolds. "Taylor and Billie spent the day by the pool at their private home," an onlooker told Us Weekly of the romantic getaway. "Taylor was taking selfies and tons of photos with Billie. He also was jumping off a high wall into the pool and Billie was marveling at him. … Billie was happy and having a fun day without a care in the world."
As the Star Wars: The Force Awakens actress (whose late mom was best known for her role as Princess Leia in the sci-fi films) mourned the losses of Fisher and Reynolds, the Twilight actor continued to stay by her side. "Taylor has been at Billie's house every day, taking care of her," a second source told Us at the time. "He's by her side constantly, trying to help her get through this. He has been trying to figure out the best way to help her cope during this difficult time."
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